Biology Chapter 5 Terms

Front 1

the movement of materials across a membrane through the use of cellular energy, normally against a concentration gradient.

Back 1

active transport

Front 2

a channel selective for water formed by proteins that span the cell membrane.

Back 2

aquaporin

Front 3

a membrane protein that facilitates the diffusion of specific substances across the membrane. The molecule to be transported binds to the outer surface of the carrier protein; the protein then changes shape, allowing the molecule to move across the membrane through the protein.

Back 3

carrier protein

Front 4

a membrane protein that forms a channel or pore completely through the membrane and that is usually permeable to one or to a few water-soluble molecules, especially ions.

Back 4

channel protein

Front 5

anchor cell membranes

Back 5

attachment proteins

Front 6

the number of particles of a dissolved substance in a given unit of volume.

Back 6

concentration

Front 7

the difference in concentration of a substance between two parts of a fluid or across a barrier such as a membrane.

Back 7

concentration gradient

Front 8

a strong cell-to-cell junction that attaches adjacent cells to one another.

Back 8

desmosome

Front 9

the net movement of particles from a region of high concentration of that particle to a region of low concentration, driven by the concentration gradient; may occur entirely within a fluid or across a barrier such as a membrane.

Back 9

diffusion

Front 10

the process in which the plasma membrane engulfs extracellular material, forming membrane-bound sacs that enter the cytoplasm and thereby move material into the cell.

Back 10

endocytosis

Front 11

a protein catalyst that speeds up the rate of specific biological reactions.

Back 11

enzyme

Front 12

the process in which intracellular material is enclosed within a membrane-bound sac that moves to the plasma membrane and fuses with it, releasing the material outside the cell.

Back 12

exocytosis

Front 13

the diffusion of molecules across a membrane, assisted by protein pores or carriers embedded in the membrane.

Back 13

facilitated diffusion

Front 14

a liquid or gas.

Back 14

fluid

Front 15

a model of membrane structure; according to this model, membranes are composed of a double layer of phospholipids in which various proteins are embedded. The phospholipid bilayer is a somewhat fluid matrix that allows the movement of proteins within it.

Back 15

fluid mosaic model

Front 16

a type of cell-to-cell junction in animals in which channels connect the cytoplasm of adjacent cells.

Back 16

gap junction

Front 17

a protein to which a carbohydrate is attached.

Back 17

glycoprotein

Front 18

a difference in concentration, pressure, or electrical charge between two regions.

Back 18

gradient

Front 19

referring to a solution that has a higher concentration of dissolved particles (and therefore a lower concentration of free water) than has the cytoplasm of a cell.

Back 19

hypertonic

Front 20

referring to a solution that has a lower concentration of dissolved particles (and therefore a higher concentration of free water) than has the cytoplasm of a cell.

Back 20

hypotonic

Front 21

referring to a solution that has the same concentration of dissolved particles (and therefore the same concentration of free water) as has the cytoplasm of a cell.

Back 21

isotonic

Front 22

the diffusion of water across a differentially permeable membrane, normally down a concentration gradient of free water molecules. Water moves into the solution that has a lower concentration of free water from a solution with the higher concentration of free water.

Back 22

osmosis

Front 23

the movement of materials across a membrane down a gradient of concentration, pressure, or electrical charge without using cellular energy.

Back 23

passive transport

Front 24

a type of endocytosis in which extensions of a plasma membrane engulf extracellular particles and transport them into the interior of the cell.

Back 24

phagocytosis

Front 25

a double layer of phospholipids that forms the basis of all cellular membranes. The phospholipid heads, which are hydrophilic, face the water of extracellular fluid or the cytoplasm; the tails, which are hydrophobic, are buried in the middle of the bilayer.

Back 25

phospholipid bilayer

Front 26

the nonselective movement of extracellular fluid, enclosed within a vesicle formed from the plasma membrane, into a cell.

Back 26

pinocytosis

Front 27

a cell-to-cell junction in plants that connects the cytoplasm of adjacent cells.

Back 27

plasmodesma

Front 28

the process by which reduced water pressure in the central vacuole of a plant cell allows the cytoplasm to shrink away from the cell wall. Plasmolysis causes soft parts of plants to wilt.

Back 28

plasmolysis

Front 29

the selective uptake of molecules from the extracellular fluid by binding to a receptor located at a coated pit on the plasma membrane and pinching off the coated pit into a vesicle that moves into the cytoplasm.

Back 29

receptor-mediated endocytosis

Front 30

a protein, located on a membrane (or in the cytoplasm), that recognizes and binds to specific molecules. Binding by receptor proteins typically triggers a response by a cell, such as endocytosis, increased metabolic rate, or cell division.

Back 30

receptor protein

Front 31

a protein or glycoprotein protruding from the outside surface of a plasma membrane that identifies a cell as belonging to a particular species, to a specific individual of that species, and in many cases to one specific organ within the individual.

Back 31

recognition protein

Front 32

the quality of a membrane that allows certain molecules or ions to move through it more readily than others.

Back 32

selectively permeable

Front 33

the diffusion of water, dissolved gases, or lipid-soluble molecules through the phospholipid bilayer of a cellular membrane.

Back 33

simple diffusion

Front 34

a substance that is dissolved in a solvent

Back 34

solute

Front 35

a liquid capable of dissolving (uniformly dispersing) other substances in itself.

Back 35

solvent

Front 36

a type of cell-to-cell junction in animals that prevents the movement of materials through the spaces between cells.

Back 36

tight junction

Front 37

a protein that regulates the movement of water-soluble molecules through the plasma membrane.

Back 37

transport protein

Front 38

pressure developed within a cell (especially the central vacuole of plant cells) as a result of osmotic water entry.

Back 38

turgor pressure